FIG. 1 illustrates an exemplary basic structure of a UMTS (Universal Mobile Telecommunications System) network according to the present invention and the related art. The UMTS includes a terminal (user equipment (UE)), a UTRAN (UMTS Terrestrial Radio Access Network), and a core network (CN). The UTRAN includes one or more radio network sub-systems (RNSs). Each RNS includes a radio network controller (RNC) and a plurality of base stations (Node-Bs) managed by the RNC. One or more cells exist for a single Node B.
FIG. 2 illustrates a radio interface protocol architecture based on a 3GPP radio access network specification between the UE and the UTRAN. As shown in FIG. 2, the radio interface protocol has horizontal layers comprising a physical layer, a data link layer, and a network layer, and has vertical planes comprising a user plane (U-plane) for transmitting data information and a control plane (C-plane) for transmitting control signals (signaling). The protocol layers in FIG. 2 can be divided into a first layer (L1), a second layer (L2), and a third layer (L3) based on three lower layers of an open system interconnection (OSI) standard model widely known in communication systems.
Each layer in FIG. 2 will be described in more detail as follows. The first layer (L1), namely, the physical layer, provides an information transfer service to an upper layer by using a physical channel. The physical layer is connected to an upper layer called a medium access control (MAC) layer via a transport channel. Data is transferred between the MAC layer and the physical layer via the transport channel. Meanwhile, between different physical layers, namely, between a physical layer of a transmitting side and that of a receiving side, data is transferred via the physical channel.
The MAC layer of the second layer provides a service to a radio link control (RLC) layer, its upper layer, via a logical channel. The RLC layer of the second layer may support reliable data transmissions and perform segmentation and concatenation on RLC service data units (SDUs) delivered from an upper layer.
A radio resource control (RRC) layer located at the lowest portion of the third layer is defined only in the control plane, and handles the controlling of transport channels and physical channels in relation to establishment, reconfiguration and release of radio bearers (RBs). The radio bearer refers to a service provided by the second layer (L2) for data transmission between the terminal and the UTRAN. In general, establishing the radio bearer refers to defining the protocol layers and the characteristics of the channels required for providing a specific service, and setting respective substantial parameters and operation methods.
When an RRC layer of a particular terminal and that of the UTRAN are connected to exchange an RRC message to each other, the corresponding terminal is in an RRC connected state, and when the RRC layer of the particular terminal and that of the UTRAN are not connected, the corresponding terminal is in an idle state. The RRC connected state of the terminal may be divided into a URA_PCH state, a CELL_PCH state, a CELL_FACH state, and a CELL_DCH state. In order to reduce power consumption, terminals in the idle state, in the URA_PCH or in the CELL_PCH state discontinuously receive a PICH (Paging indicator Channel), a physical channel, and an SCCPCH (Secondary Common Control Physical Channel), a physical channel, to which a PCH (Paging Channel), a transport channel, is mapped, by using a DRX (Discontinuous Reception) method. During other time intervals than the time duration while the PICH or the SCCPCH is received, the terminal is in a sleeping mode. In the related art, the terminal performing the DRX method wakes up at every CN domain specific DRX cycle length or at every UTRAN specific DRX cycle length to receive a terminal-exclusive PI (Paging Indicator). Here, the terminal-exclusive PI in the related art is used to inform a particular terminal that a paging message will be transmitted to the particular terminal via the PCH channel. The PICH channel is divided into 10 ms-long PICH frames, and a single PICH frame consists of 300 bits. The first 288 bits of a single frame are used for the terminal-exclusive PICH to transmit one or more terminal-exclusive Pls. The rear 12 bits of the single PICH frame are not transmitted. For the sake of convenience, the portion of the front 288 bits of the PICH channel is defined as a UE PICH, and the portion of the rear 12 bits is defined as a PICH unused part.
FIG. 3 is a signal flow chart illustrating an RRC connection procedure between the terminal and the UTRAN according to the related art. As shown in FIG. 3, in order for the terminal in the idle state to be RRC-connected with the UTRAN, the terminal should perform an RRC connection procedure. The RRC connection procedure may include three steps: transmitting, by the terminal, an RRC connection request message to the UTRAN (S1); transmitting, by the UTRAN, an RRC connection setup message to the terminal (S2); and transmitting, by the terminal, an RRC connection setup complete message to the UTRAN (S3).
An HS-DSCH transmission for transmitting high speed data to a single terminal via the downlink in the related art will now be described. The HS-DSCH has a 2 ms transmission time interval (TTI) (3 slots) and supports various modulation code sets (MCSs) to obtain a high data rate. An optimum throughput may be achieved by selecting an MCS which is most suitable for a channel situation. For this, a hybrid automatic repeat request (HARQ) technique that combines an ARQ technique and a channel coding technique can be employed to perform reliable transmissions.
FIG. 4 illustrates a protocol stack of the HS-DSCH according to the related art. As shown in FIG. 4, a data unit transferred from an RLC layer of an SRNC is delivered to a MAC-d entity that manages a dedicated channel via a DICH or a DCCH, a logical channel, and the corresponding data is transferred to a MAC-hs of a Node B via a MAC-c/sh/m of an CRNC. Here, the MAC-d is a MAC entity that manages the dedicated channel, the MAC-c/sh/m is a MAC entity that manages a common channel, and a MAC-hs is a MAC entity that manages the HS-DSCH.
A physical channel HS-PDSCH is used to transmit the transport channel HS-DSCH. The HS-PDSCH has a fixed 16 spreading factor and corresponds to a channelization code selected from a set of channelization codes reserved for HS-DSCH data transmission. If a multi-code transmission is performed with respect to a single UE, a plurality of channelization codes are allocated during the same HS-PDSCH sub-frame. FIG. 5 illustrates a sub-frame and slot structure of the HS-PDSCH. The HS-PDSCH transmits QPSK or 16 QAM modulation symbols. In FIG. 5, ‘M’ indicates the number of bits per modulation symbol. Namely, in case of QPSK, ‘M’ is 2, and in case of 16QAM, ‘M’ is 4.
FIG. 6 illustrates a channel configuration according to the related art.
As shown in FIG. 6, in order to transmit user data via the HS-DSCH, HS-DSCH control information needs to be transmitted, and in this case, the HS-DSCH control information is transmitted via a downlink HS-SCCH (High Speed-Shared Control Channel) and an uplink HS-DPCCH (High Speed-Dedicated Physical Control Channel). Here, a DPCH (Dedicated Physical Channel) is a bi-directional physical channel, to which the transport channel DCH is mapped, and is used to transfer terminal-exclusive data and terminal-exclusive L1 control information such as a power control signal required for controlling closed-loop power. In addition, an F-DPCH (Fractional Dedicated Physical Channel), a downlink channel, is a physical channel that transmits several DPCHs by using a single channel code. Here, a single F-DPCH does not transmit terminal-exclusive (or terminal dedicated) data of several terminals but is used to transfer terminal-exclusive L1 control information of several terminals, such as the power control signal required for controlling the closed-loop power, together. If there is a downlink F-DPCH channel, an uplink DPCH channel also operates in conjunction. In FIG. 6, a UE1, a UE2 and a UE3 use the F-DCPH via a single channel code and, in this case, each terminal provides the DPCH upwardly.
The downlink HS-SCCH, a downlink physical channel, is transmitted with a spreading factor 128 and has a 60-kbps transfer rate. FIG. 7 illustrates a sub-frame structure of the HS-SCCH. Information transmitted via the downlink HS-SCCH may be roughly divided into transport format and resource related information (TFRI) and HARQ-related information, and in addition, UE identifier (namely, an H-RNTI (HS-DSCH Radio Network Temporary Identifier)) information for providing information about a particular user is masked thereto and then transmitted. Table 1 shows detailed HS-SCCH information.
TABLE 1TFRI informationChannelization-code-set informationxccs, 1, xccs, 2 . . . Xccs, 7(7 bits)Modulation scheme information (1 bit)xms, 1Transport-block size information (6 bits)Xtbs, 1, xtbs, 2, . . . Xtbs, 6HARQ informationHybrid-ARQ process information (3 bits)xhap, 1, xhap, 2, xhap, 3Redundancy and constellation versionxrv, 1, xrv, 2, xrv, 3(3 bits)New data indicator (1 bit)xnd, 1UE ID informationUE identity (16 bits)xue, 1, xue, 2, . . . xue, 16
FIG. 8 shows a coding scheme of the HS-SCCH based on the above information.
The uplink HS-DPCCH transmits an uplink feedback signaling related to downlink HS-DSCH data transmission. The HS-DPCCH, a dedicated channel for a particular terminal, operates cooperatively with the uplink and downlink DPCHs. The feedback signaling includes ACK (Acknowledgement)/NACK (Negative Acknowledgement) information for the HARQ and a CQI (Channel Quality Indicator). A frame of the HS-DPCCH includes five sub-frames. Each sub-frame has a length of 2 ms, and a single sub-frame includes the first to third slots, namely, the three slots. Each slot of the sub-frames carries the following information: HARQ ACK/NACK information is transmitted on the first slot of the sub-frames of the HS-DPCCH; and the CQI is transmitted on the second and third slots of the sub-frames of the HS-DSCH. The HS-DPCCH is transmitted always together with an uplink PDCCH. The CQI transfers status information of a downlink radio channel obtained from the results of the UE's measurement of a downlink CPICH (Common Pilot Channel), and the ACK/NACK provides ACK or NACK information regarding a user data packet which has been transmitted via the downlink HS-DSCH according to the HARQ mechanism. FIG. 9 illustrates a frame structure of the uplink HS-DPCCH.
The problem to be solved by the present invention is as follows.
In the related art, when the terminal is in the CELL_DCH state, the terminal can receive the HS-DSCH. Meanwhile, if the terminal is in the CELL_FACH, the CELL_PCH, the URA_PCH or idle state, besides the CELL_DCH state, the terminal cannot receive the HS-DSCH but receive the FACH or the PCH which is mapped to the SCCPCH. In this respect, however, compared with the HS-DSCH, AMC (Adaptive Modulation and Coding) cannot be applied for the FACH and the PCH, so in terms of efficiency of radio resources, the FACH and the PCH are considered to be inefficiently used channels.
Thus, in the related art, in order to apply the AMC in other states (namely, CELL_FACH, the CELL_PCH, the URA_PCH and idle mode states) than the CELL_DCH state, AMC information should be added to a TFCI (Transport Format Combination Indicator) that transfers control information for the FACH and the PCH. This, however, causes a problem in that the related art terminal cannot recognize the TFCI.